The crayfish have its nerve cord on the ventral side rather than on the dorsal side. The ventral side is under the Crayfishes' exoskeleton, as opposed to the dorsal side where the exoskeleton is . If it is attacked it will be from the dorsal side and the nerve cord would be snapped easier. The function of the nerve cord is that if it gets attacked by a predator they will go for the top and it will still be able to move.
we have been evolved through same root, during the process we get separated and develop new features to adjust in the surrounding atmosphere, that's why our genes are matching with fruit flies and others.
Not all of those offspring are likely to live to adulthood, whereas the parent penguin can pay attention to the one chick it has so it is more likely to live to adulthood
